TRACE Tree Rings Archaeology Climatology Ecology

Dendroecological analysis of vegetation dynamics on
abandoned heath lands in the Svabian Jura,
southern Germany
M. Wegst & A. Bräuning
Institut für Geographie, Azenbergstr. 12, 70174 Stuttgart, Germany; e-mail: mwegst@gmx.de;
achim.braeuning@geographie.uni-stuttgart.de
Introduction
The preservation of floristically rich vegetation types of heath landscapes (Gentiano-
Koelerietum) that evolved during centuries of formerly practised extensive land use as
pasture is presently a tremendous problem for nature conservation (Beinlich & Plachter
1995; Schreiber 1997). After abandonment due to economic changes during the last
decades, succession processes take place that include the re-immigration of woody species
and the gradual displacement of rare herbs. However, the dynamic of these processes can
not be satisfactorily documented and analysed by means of plant sociological investigations,
since species of former pasture lands mix with invading woody species. Long-term
observations or repetitive mapping are not practicable and cost-effective. Furthermore, it has
to be considered that the spatial pattern of shrub distribution largely depends on the different
distribution strategies of the invading species. The dendroecological analysis of shrubs does
not only allow the exact age determination and hence the establishment of all individuals
during the process of invasion, but also enables the reconstruction of species-specific
propagation patterns.
Material and Methods
The immigration patterns of invasive woody species were analysed on 4 study plots in the
valley of the “Grosse Lauter” in the jurrassic limestone mountain area of the Svabian Alb. All
study plots have comparable ecological conditions concerning soil conditions (rendzic
leptosols) and former land use as pasture. The exact locations of all individuals on the
sampling plots were determined and mapped with the help of a Geographic Information
System (ARC View). Stem discs of all individuals on each plot were gained by cutting the
shrubs at their base. Larger individuals were cored obliquely at a height of 30 cm to reach
the oldest annual rings at the base. After drying, the surfaces of the cross sections were
smoothed by sanding or by cutting with razor blades and the numbers of annual rings were
counted. Additionally, microtome slices were prepared for selected samples (Schweingruber
2001). In total, 719 individuals of 18 woody species (among them 13 tree species) were
examined.
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